Cluster: new option to work with partial slots coverage.
Cluster: claim ping_sent time even if we can't connect.

This fixes a potential bug that was never observed in practice since
what happens is that the asynchronous connect returns ok (to fail later,
calling the handler) every time, so a ping is queued, and sent_ping
happens to always be populated.

Howver technically connect(2) with a non blocking socket may return an
error synchronously, so before this fix the code was not correct.
Unix domain sockets incorrectly listed as IPv6.
Merge pull request #2010 from yossigo/unixdomain-info-string

Unix domain sockets incorrectly listed as IPv6.
anetPeerToString() refactoring and more explicit checks.

Related to PR #2010.
Improve disable save comment in redis.conf

Closes #1897
Remove surplus double quotes

Closes #1877
Update linenoise accessory files

The core linenoise code was being backported, but not
the README or example.  It's less confusing for users
if everything matches across directories.

Fix inspired by @thrig

Closes #1872
Fix many small typos

Closes #1871
Fix incorrect comments

error != success; and 0 != number of bytes written

Closes #1806
Fix typo in redis.conf

Closes #1713
Fix typo

Closes #1682
Fix typo in 00-RELEASENOTES

Closes #1673
Fix typo

Closes #1544
Fix typo: ad -> and

Closes #1537
Fix typos

Closes #1513
Grammar and typo fixes in redis.conf

Closes #1441
Fix typo in redis.h

Closes #1386
Fix on-place -> in-place

Closes #1373
Fix hash table size in comment for dictScan

Closes #1351